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  #11  
Old 11-24-2019, 09:40 PM
mantry mantry is offline
 
Join Date: May 2014
Location: Bountiful, UT
Posts: 145
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In some of the Cessna tailwheel circles it is thought that the tailwheel shimmy is caused by the geometry of the tailwheel in relation to the ground.

Take a look at this: https://backcountrypilot.org/forum/i...eel-shimmy-687

Mark
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  #12  
Old 11-25-2019, 03:12 AM
74-07 74-07 is offline
 
Join Date: Dec 2016
Location: Greenville, SC
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Sorry for the misunderstanding. Yes, I have the original Van's yoke
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  #13  
Old 11-25-2019, 03:02 PM
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vfrazier vfrazier is offline
 
Join Date: Jan 2007
Location: Mount Vernon, IN
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Not implying that anyone has this problem, but watch out for bent rod springs. If the tailwheel pivot shaft is leaning forward too much, at some point shimmy becomes inevitable.

Our Stinson was loads of fun when the tailspring became bent (I blame my partner, but it was just normal wear and tear.) After fixing the spring, it was a pussycat again with no more shimmy.

Interesting too... what one person calls a "yoke" others, like us, call a "mounting socket". Either name should work as long as we all know what part we're talking about!
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  #14  
Old 11-25-2019, 03:48 PM
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Mark Dickens Mark Dickens is offline
 
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Location: Collierville, TN (KFYE)
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Quote:
Originally Posted by RV8JD View Post
Mark,

Which TW yoke do you have (i.e, original Van's or the JDAir bearing yoke)? And do you have chains or a steering arm?


Rob (74-07),

Which TW yoke do you have?

Thx.
I bought a new fork at the same time with the wheel...I have springs
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  #15  
Old 04-28-2020, 01:23 PM
Docbru Docbru is offline
 
Join Date: Nov 2012
Location: Ontario, Canada
Posts: 23
Default Condor 2 tailwheel

I had this setup sitting in a box at the hangar for months and finally got around to installing it on my RV 8 and testing it. It was a straight forward swap with the stock tailwheel. Taxi testing showed no change in the steering capabilities and it provided a much smoother ride over bumps and cracks compared to the solid rubber tailwheel. I?m running 45-50 psi. Directional control during take-off and landing was no different. It might be my imagination but I think during landing when the tailwheel came down there was a slightly ?softer? feel...I always wheel land and hold the tail up as long as possible. It is a quality piece as I?ve come to expect from Flyboys. 5 stars.
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  #16  
Old 06-25-2020, 03:34 PM
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mike newall mike newall is offline
 
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Location: Yorkshire, England
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2 of us in the UK have just fitted the same set up and now both having big shimmy issues.

Contacted Blake - fab service as usual - he sent lots of info.

Ours is a 10 year old 500 hour spring/knuckle on a Rocket Lynx steering set up. I have ordered a new spring, knuckle and steering arm, but it wont arrive for a month as it is sea freight.

Going back to the old tailwheel and will report back when the new one is installed. We have our tyre at 50 psi and I have put tyre jizz into it to help the loss of pressure.
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  #17  
Old 06-26-2020, 02:46 AM
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mike newall mike newall is offline
 
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I think the problem is a compound one.

The yoke is longer (taller), the tyre is larger so the knuckle angle changes - better viz etc, but takes the whole assembly into shimmy territory. Add in an old stinger that has sagged a bit and away we go.

Has anyone bent a stinger, either by annealing, bending and re tempering, or just by cold bending ?

Is the 14 stinger a different part ?

Scott - if you pick up on this, your input would be welcome please.
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  #18  
Old 06-26-2020, 05:06 AM
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F1Boss F1Boss is offline
 
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Location: Taylor Texas
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Default Spring re-shaping

Heat the spring until it is just starting to turn red where you want the bend, then bend. You will not remove the temper. Piece ?o cake!
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  #19  
Old 06-26-2020, 06:07 AM
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mike newall mike newall is offline
 
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Thanks for that - will give it a whirl.
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  #20  
Old 06-26-2020, 03:36 PM
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BlakeFrazier BlakeFrazier is offline
 
Join Date: Mar 2016
Location: Evansville, IN
Posts: 61
Default Addressing shimmy issues

Howdy folks... writing up a document to address the topic of tailwheel shimmy has been on my do-list for some time. Thanks for giving me the extra incentive to get it knocked out! I've created a post on our blog, which aggregates information from several other posts on the topic and applies it directly to RVs.

Link to the full article here: http://flyboyblog.com/2020/06/26/add...shimmy-in-rvs/

The short synopsis goes like this:
- Tailwheel geometry is the biggest contributing factor to shimmy
- Fixing the tailwheel geometry can be fairly easy and low cost.
- Another VAF user has discussed a method for putting a bend in the tail spring to improve the steering angle geometry, with good results (link here)


This is the geometry we're shooting for.

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